@article{fdi:010079839,
  title = {{W}hy do {B}enguela {N}inos lead {A}tlantic {N}inos ?},
  author = {{I}llig, {S}erena and {B}achelery, {M}. {L}. and {L}ubbecke, {J}. {F}.},
  editor = {},
  language = {{ENG}},
  abstract = {{W}e investigate the lag between warm interannual {S}ea {S}urface {T}emperature ({SST}) events in the eastern-equatorial {A}tlantic, the {A}tlantic {N}inos, and the occurrence of {B}enguela {N}inos along the southwestern {A}ngolan coast. {W}hile it is commonly agreed that both events are associated with equatorial and subsequent coastal-trapped wave propagations driven remotely by a relaxation of the trade-winds, it is surprising that {SST} anomalies off {A}ngola tend to precede the ones in the eastern-equatorial sector by similar to 1 month. {T}o explain this counterintuitive behavior, our methodology is based on the experimentation with a {T}ropical {A}tlantic {O}cean model. {U}sing idealized wind-stress perturbations from a composite analysis, we trigger warm equatorial and coastal events over a stationary and then, seasonally varying ocean mean-state. {I}n agreement with the linear dynamics, our results show that when the interannual wind-stress forcing is restricted to the western-central equatorial {A}tlantic, the model yields equatorial events leading the coastal ones. {T}his implies that neither the differences in the ocean stratification between the two regions (thermocline depths or modal wave contributions) nor the seasonal phasing of the events explains the observed temporal sequence. {O}nly if wind-stress anomalies are also prescribed in the coastal fringe, the coastal warming precedes the eastern-equatorial {SST} anomaly peak, emphasizing the role of the local forcing in the phenology of {B}enguela {N}inos. {A} weaker {S}outh-{A}tlantic {A}nticyclone initiates the coastal warming before the development of eastern-equatorial {SST} anomalies. {T}hen, equatorward coastal wind anomalies, driven by a convergent anomalous circulation located on the warm {A}tlantic {N}ino, stop the remotely forced coastal warming prematurely. {P}lain {L}anguage {S}ummary {W}e investigate the {S}ea {S}urface {T}emperature ({SST}) interannual fluctuations in the {T}ropical {A}tlantic. {W}e focus on the extreme warm events that occur every few years in the {G}ulf of {G}uinea, the {A}tlantic {N}inos, and along the coast of {A}ngola-{N}amibia, the {B}enguela {N}inos. {I}t is commonly agreed that both events are forced by equatorial and subsequent coastal waves triggered in the western-central basin by a relaxation of the trade-winds. {Y}et, we observe that the coastal warming tends to precede the one in the {G}ulf of {G}uinea by similar to 1 month. {W}e explain this counterintuitive fact, using experimentation with a {T}ropical {A}tlantic {O}cean model. {U}sing idealized wind-stress perturbations, we simulate warm equatorial and coastal events on top of a stationary and then, seasonally varying ocean mean-state. {R}esults show that when wind-stress perturbations are confined to the western-central equatorial {A}tlantic, the model yields equatorial events leading the coastal variability, consistent with the propagation path of the waves. {T}his implies that neither the ocean mean-state nor its seasonal variability controls the timing between events. {W}e further show that only when wind-stress anomalies are prescribed within the coastal fringe, warm events off {A}ngola precede the eastern-equatorial {SST} anomaly. {B}oth warmings originate from a reduction of the strength of the {S}outh-{A}tlantic {A}nticyclone. {N}evertheless, local processes initiate the coastal warming before the remotely forced equatorial waves impact the eastern-equatorial {SST}. {B}enguela {N}inos then also stop earlier due to the development of coastal wind anomalies associated with a convergent anomalous circulation located on the warm {A}tlantic {N}ino event.},
  keywords = {{ATLANTIQUE} ; {ZONE} {TROPICALE} ; {BENGUELA} {COURANT} ; {GUINEE} {GOLFE}},
  booktitle = {},
  journal = {{J}ournal of {G}eophysical {R}esearch : {O}ceans},
  volume = {125},
  numero = {9},
  pages = {e2019{JC}016003 [27 ]},
  ISSN = {2169-9275},
  year = {2020},
  DOI = {10.1029/2019jc016003},
  URL = {https://www.documentation.ird.fr/hor/fdi:010079839},
}